In a variable-capacity turbocharger, a nozzle blade is annularly arranged in a plurality in the periphery of a turbine impeller, and the capacity of the turbine is changed by adjusting the nozzle opening by the rotation angle of these nozzle blades.
It is known that when the shape of the nozzle blades that are arranged on the periphery of this kind of turbine impeller is changed, the flow of exhaust gas that is supplied to the turbine impeller changes in conjunction with shape changes of the nozzle blades, and the turbine efficiency changes.
For example, Patent Document 1 discloses a nozzle blade in which the leading edge shape and the trailing edge shape are curved in the blade height direction (rotation axis direction).
In greater detail, in Patent Document 1, the leading edge shape and the trailing edge shape of the nozzle blade are set so as to curve so that the center in the blade height direction is concave toward the rotation axis side. Accordingly, the turbine efficiency increases.